freebsd-dev/sys/dev/random/live_entropy_sources.c
Mark Murray 10cb24248a This is the much-discussed major upgrade to the random(4) device, known to you all as /dev/random.
This code has had an extensive rewrite and a good series of reviews, both by the author and other parties. This means a lot of code has been simplified. Pluggable structures for high-rate entropy generators are available, and it is most definitely not the case that /dev/random can be driven by only a hardware souce any more. This has been designed out of the device. Hardware sources are stirred into the CSPRNG (Yarrow, Fortuna) like any other entropy source. Pluggable modules may be written by third parties for additional sources.

The harvesting structures and consequently the locking have been simplified. Entropy harvesting is done in a more general way (the documentation for this will follow). There is some GREAT entropy to be had in the UMA allocator, but it is disabled for now as messing with that is likely to annoy many people.

The venerable (but effective) Yarrow algorithm, which is no longer supported by its authors now has an alternative, Fortuna. For now, Yarrow is retained as the default algorithm, but this may be changed using a kernel option. It is intended to make Fortuna the default algorithm for 11.0. Interested parties are encouraged to read ISBN 978-0-470-47424-2 "Cryptography Engineering" By Ferguson, Schneier and Kohno for Fortuna's gory details. Heck, read it anyway.

Many thanks to Arthur Mesh who did early grunt work, and who got caught in the crossfire rather more than he deserved to.

My thanks also to folks who helped me thresh this out on whiteboards and in the odd "Hallway track", or otherwise.

My Nomex pants are on. Let the feedback commence!

Reviewed by:	trasz,des(partial),imp(partial?),rwatson(partial?)
Approved by:	so(des)
2014-10-30 21:21:53 +00:00

191 lines
5.3 KiB
C

/*-
* Copyright (c) 2013 Arthur Mesh <arthurmesh@gmail.com>
* Copyright (c) 2013 Mark R V Murray
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer
* in this position and unchanged.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/param.h>
__FBSDID("$FreeBSD$");
#include "opt_random.h"
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/queue.h>
#include <sys/random.h>
#include <sys/sbuf.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/unistd.h>
#include <machine/cpu.h>
#include <dev/random/randomdev.h>
#include <dev/random/randomdev_soft.h>
#include <dev/random/random_adaptors.h>
#include <dev/random/random_harvestq.h>
#include "live_entropy_sources.h"
/*
* The les_lock protects the consistency of the "struct les_head les_sources"
*/
static struct sx les_lock; /* Need a sleepable lock for the sbuf/sysctl stuff. */
LIST_HEAD(les_head, live_entropy_sources);
static struct les_head les_sources = LIST_HEAD_INITIALIZER(les_sources);
void
live_entropy_source_register(struct live_entropy_source *rsource)
{
struct live_entropy_sources *lles;
KASSERT(rsource != NULL, ("invalid input to %s", __func__));
lles = malloc(sizeof(*lles), M_ENTROPY, M_WAITOK);
lles->lles_rsource = rsource;
sx_xlock(&les_lock);
LIST_INSERT_HEAD(&les_sources, lles, lles_entries);
sx_xunlock(&les_lock);
}
void
live_entropy_source_deregister(struct live_entropy_source *rsource)
{
struct live_entropy_sources *lles = NULL;
KASSERT(rsource != NULL, ("invalid input to %s", __func__));
sx_xlock(&les_lock);
LIST_FOREACH(lles, &les_sources, lles_entries)
if (lles->lles_rsource == rsource) {
LIST_REMOVE(lles, lles_entries);
break;
}
sx_xunlock(&les_lock);
if (lles != NULL)
free(lles, M_ENTROPY);
}
static int
live_entropy_source_handler(SYSCTL_HANDLER_ARGS)
{
struct live_entropy_sources *lles;
struct sbuf sbuf;
int error, count;
sx_slock(&les_lock);
sbuf_new_for_sysctl(&sbuf, NULL, 64, req);
count = 0;
LIST_FOREACH(lles, &les_sources, lles_entries) {
sbuf_cat(&sbuf, (count++ ? ",'" : "'"));
sbuf_cat(&sbuf, lles->lles_rsource->les_ident);
sbuf_cat(&sbuf, "'");
}
error = sbuf_finish(&sbuf);
sbuf_delete(&sbuf);
sx_sunlock(&les_lock);
return (error);
}
/*
* Run through all "live" sources reading entropy for the given
* number of rounds, which should be a multiple of the number
* of entropy accumulation pools in use; 2 for Yarrow and 32
* for Fortuna.
*
* BEWARE!!!
* This function runs inside the RNG thread! Don't do anything silly!
*/
/* XXXRW: get_cyclecount() is cheap on most modern hardware, where cycle
* counters are built in, but on older hardware it will do a real time clock
* read which can be quite expensive.
*/
void
live_entropy_sources_feed(void)
{
static struct harvest_event event;
struct live_entropy_sources *lles;
int i, read_rate;
u_int n;
sx_slock(&les_lock);
/*
* Walk over all of live entropy sources, and feed their output
* to the system-wide RNG.
*/
read_rate = random_adaptor_read_rate();
LIST_FOREACH(lles, &les_sources, lles_entries) {
for (i = 0; i < harvest_pool_count*read_rate; i++) {
/* This *must* be quick, since it's a live entropy source. */
n = lles->lles_rsource->les_read(event.he_entropy, HARVESTSIZE);
KASSERT((n > 0 && n <= HARVESTSIZE), ("very bad return from les_read (= %d) in %s", n, __func__));
memset(event.he_entropy + n, 0, HARVESTSIZE - n);
event.he_somecounter = get_cyclecount();
event.he_size = n;
event.he_bits = (n*8)/2;
event.he_source = lles->lles_rsource->les_source;
event.he_destination = harvest_destination[event.he_source]++;
/* Do the actual entropy insertion */
harvest_process_event(&event);
}
}
sx_sunlock(&les_lock);
}
void
live_entropy_sources_init(void)
{
SYSCTL_PROC(_kern_random, OID_AUTO, live_entropy_sources,
CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
NULL, 0, live_entropy_source_handler, "",
"List of Active Live Entropy Sources");
sx_init(&les_lock, "live_entropy_sources");
}
void
live_entropy_sources_deinit(void)
{
sx_destroy(&les_lock);
}